GTA 2 nyc.gci Handling & Physics

Cars are just 2D images in GTA2. Driving them is more like moving something in an image editor!

During the past decade I have tried several times to understand GTA2 physics. A few things do work reliably and this page is about them. The rest is a mystery!

Differences in the .sty File

Even if you use exact same settings in nyc.gci for two cars, they might have very different performance when turning. The acceleration would be the same but that’s it.

This is due to the Collision Size, the position of Front Wheels and the position of Rear Wheels. Sty Tool by Delfi/JernejL has an Edit Car button where you can change these. Drag the red lines to change wheel positions; double-click the car preview to change Collision Size.

Even a 1 pixel difference in wheel position creates a measurable difference in handling when playing GTA2. If you drive in a constant circle, both the radius of the circle and the speed of the vehicle change. (This is logical; the same happens with rear cars.)

When the Collision Size is different, it slightly offsets the wheel positions.

Wheel Positions

Move Forwards

Move Rearwards

Front Wheels

Tighter turn, lower speeds.

Rear Wheels

Wider turn, higher speed.

Collision Size

Smaller

Bigger

Width

Not tested.

Not tested.

Height

Tighter turn, lower speed.

Not tested.

Viewing the Handling File

Your gta2\data folder has a file called nyc.gci which contains the handling for every car in every level. Make a backup of this before you start changing any values!

You can open the file with Notepad. Read the instructions at the bottom of my Tools & Editors for GTA 2 list. You can also use the GTA2 Power Manager. t adds a Physics tab which lists all the cars. Selecting a car loads all its handling values into boxes with sliders.

To get a good overview and compare the data, you have to see lots of cars at the same time with the data nicely aligned. So I turned the data into a spreadsheet, which you can download here:

Opens with any spreedsheet program (like Microsoft Excel) or text editor (like Notepad). Includes the original handling, so you can restore your changes easily.

Acceleration

Each gear has an acceleration curve. They start by accelerating very fast but this reduces a lot as the speed increases. You can only reach top speed in 3rd gear if the curves overlap. The Dementia sometimes won’t reach 3rd gear because the overlap is very small.

Relevant Settings

Several values affect acceleration and top speed:

Thrust

The power of the engine.

Turbo

Increases power when at higher engine speeds (rpm).

Gear n Multiplier

This value increases power and speed at the same time. Not like the gear ratios in a real car!

Rear Stability

Yes, this actually has a big effect. Bigger values make the car slower. Did I mention GTA2 physics are weird?

The max_speed value sets a limit on the top speed. The car can only reach this speed if the other settings are correct. A car cannot go faster than the max_speed value.

Realistic Performance

You should make 1st gear quite powerful but never as powerful as 3rd. 2nd gear can be quite close to 1st. Make sure 2nd lets you go fast enough to reach 3rd!

It is quite nice to set 3rd gear so you only just reach top speed. Then the car will accelerate gradually when you are at high speed. You must carry speed through the corners and a take good racing line to reach the highest speed, a bit like real racing.

AI Handling

For the most part, this is hard-coded and ignores the actual handling of the vehicles. It uses a basic mode which makes the cars very agile.

(That’s why the AI can make the Bus can turn on a sixpence. This probably makes the traffic less CPU intensive, since you don’t need Gran Turismo levels of cleverness in the computer drivers.)

Elypter discovered there are some shared settings which affect this basic mode:

You can change it globally in .gci file.

It’s one of the Hot Dog Dummy models.

You can check it in Blast City: Awkward Cargo (bc-ac).

You can also reduce brake power.

You can also check Tiny Tiny Town Army.

I reduced the break power and increased traffic speed there. So it’s more risky to walk on a street.